1. Field of the Invention
The present invention pertains to the field of fibers of synthetic polymer materials, which are suited for replacing the cellulose fibers in the manufacture of paper.
2. Description of the Prior Art
The production of fibers of synthetic polymer materials, having such characteristics as to be suited, without previous cutting or disgregating operations, for replacing at least partially the cellulose fibers in the manufacture of paper, is known.
However, the various methods which have been employed in the past for said production, proved to be so expensive as to make of the preparation of paper from such fibers an unprofitable proposition.
Thus, in U.S. Pat. Nos. 2,999,788 and 2,988,782 there are described processes for the preparation of fibrous particles of a very thin thickness and 10 to 100.mu. in length, commonly called fibrils or fibrids, which processes consist in gradually adding a synthetic polymer solution to precipitating agents for the polymer, under simultaneous heavy stirring. This process is however limited to the use of condensation polymers; moreover the microfibers thus prepared, due to their high cost, do not find a practical use, in spite of their interesting characteristics.
Quite recently there was suggested the preparation of fibrils of olefin polymers directly during the polymerization of the monomers (reactor fibers), this latter being carried out in the presence of suitable solvents and by keeping up a stirring exerting high shearing forces.
A process of this type is disclosed in British Pat. No. 1,287,917. The fibrils obtained through it, with a length varying from a few tenths of a micron to some millimeters, are particularly suited for being incorporated in the paper pulps in various percentages, and their characteristics allow their treatment by means of the standard paper processing machinary. The process herein above described has, however, the drawback of requiring special reactors expressly designed for this process (since the standard reactors for the polymerization of olefins are unsuited for the purpose) and only useable for this particular production.